Physical Electronics deals with various aspects of physical electronics, with emphasis on electron optics, heavy current electron beams, and theory and design principles of gridded valves. A paraxial theory of electrostatic and magnetic lenses is presented, and cathode imaging and electron mirrors are discussed. Electron beams in field free space are also considered, along with cylindrical diodes and planar triodes. Comprised of three sections, this volume begins with an overview of the theory of electron optics, paying particular attention to aberrations, thermal velocities, and electron beam deflection as well as cathode imaging and electron mirrors. A paraxial theory of electrostatic and magnetic lenses is also described. The next section is devoted to heavy current electron beams and looks at concepts such as dimensional scaling, electron guns, and anode aperture effects, together with Brillouin focusing of a cylindrical beam and focusing in confined flow. The final section deals with the theory and design principles of gridded valves and considers the electrostatic problem; approximations for real triodes; multigrid receiving valves; and electron-optical principles in valves. This book will be of interest to students and practitioners of physics and electronics engineering.